1. Field of the Invention
This invention relates to a focus detecting apparatus in a camera or the like.
2. Related Background Art
There is known a focus detecting apparatus of the pupil division imaging type in which an object image formed by a pair of light beams coming from the pair of different areas of the exit pupil of a photo-taking optical system is formed as a pair of object images on the pair of light receiving portions of a sensor by a focus detecting optical system having a pair of re-imaging lenses, a pair of object image signals produced by the sensor are calculation-processed to thereby calculate the amount of relative deviation of the pair of object images and the defocus amount between the imaging plane of the photo-taking optical system and the surface of film is detected on the basis of said amount of deviation.
This system has a merit that highly accurate focus detection can be effected by the pitch of sensor pixels for spatially sampling the re-imaged object being made fine, but it suffers from a demerit that a relatively large space is required for re-imaging the object image.
There is also known a focus detecting apparatus of the pupil division type but yet of the non-re-imaging type disclosed in Japanese Laid-Open Patent Application No. 54-159259. In this system, the shape of a pair of light receiving elements is projected onto the photo-taking optical system side by a plurality of minute lenses (lenslets) disposed near the surface of film and the pair of light receiving elements disposed behind them to thereby effect pupil division and the object image is spatially sampled by the plurality of lenslets, and the amount of relative deviation of the set of outputs of one of the pair of light receiving elements and the set of outputs of the other of the pair of light receiving elements is calculated, and the defocus amount between the imaging plane of the photo-taking optical system and the surface of the film is detected on the basis of said amount of deviation.
This system has a merit that a relatively small space is only required because it is not necessary to re-image the object image, but it suffers from a demerit that it is technically difficult to make the pitch of the lenslets for spatially sampling the object image fine and insensitive zones are created between the lenslets and therefore highly accurate focus detection cannot be effected.
Where a plurality of focus detection modules of said pupil division re-imaging type are disposed in the photographing image field to effect focus detection in the plurality of areas of the photographing image field, highly accurate focus detection can be effected in each focus detection area, but since a very large space is required, it has been impossible to make a camera body or the like containing the plurality of focus detection modules therein into a practically reasonable size.
Also, where a plurality of focus detection modules of said pupil division non-re-imaging type are disposed in the photographing image field to effect focus detection in the plurality of areas of the photographing image field, it is possible to make a camera body or the like containing the plurality of focus detection modules therein into a practically reasonable size, but it has been impossible to effect highly accurate focus detection in each focus detection area.